The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Ana Deletic - One of the best experts on this subject based on the ideXlab platform.
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The effect of intermittent drying and wetting stormwater cycles on the nutrient removal performances of two vegetated biofiltration designs.
Chemosphere, 2020Co-Authors: Yaron Zinger, Tim D. Fletcher, Kefeng Zhang, Veljko Prodanovic, Ana DeleticAbstract:Vegetated biofiltration systems (biofilters) are now a well-established technology for treatment of urban stormwater, typically showing high nutrient uptake. However, the impact of high temporal variability of rainfall events (further exacerbated by climate change) on nitrogen and phosphorus removal processes, within different biofiltration designs, is still unknown. Hence, a laboratory-based study was conducted to uncover mechanisms behind nutrient removal in biofilters across different drying and wetting regimes. Two sets of experimental columns were based on (1) the standard biofiltration design (unsaturated Zone only), and (2) combination of unsaturated and saturated (Submerged) Zone (SZ) with additional carbon source. Columns were watered with synthetic stormwater according to three drying and wetting schemes, exploring 1, 2, 3, 4 and 7-week drying. Hydraulic performance, soil moisture and pollutant removal were monitored. The results show that hydraulic conductivity of SZ design experiences less change over time compared to standard design, due to slower media drying, crack formation and lower plant die-off. Varied drying lengths challenged both designs differently, with 2-week drying resulting in significant drop of performance across most pollutants in standard design (except ammonia), while SZ design was able to retain high performance for up to four weeks of drying, sustaining microbial and plant uptake. Increased oxygenation of SZ columns during short-term drying was beneficial for ammonia and phosphorus removal. While SZ design showed better performance and quicker recovery for nitrogen removal, in regions with inter-rain event shorter than two weeks, the standard design (no saturated Zone, no carbon source) can achieve similar if not better results.
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The impact of stormwater biofilter design and operational variables on nutrient removal - a statistical modelling approach.
Water research, 2020Co-Authors: Kefeng Zhang, G I Chandrasena, Tracey Pham, Emily Payne, Ana Deletic, David Thomas Mccarthy, Yizhou Liu, Belinda E. Hatt, Behzad JamaliAbstract:Abstract Biofiltration systems can help mitigate the impact of urban runoff as they can treat, retain and attenuate stormwater. It is important to select the optimal design characteristics of biofilters (e.g., vegetation, filter media depth) to ensure high treatment performance. Operational conditions (e.g., infiltration rate) can also lead to significant changes in biofilter treatment performance over time. The impact of specific operational conditions on water quality treatment performance of stormwater biofilters is still not well understood. Furthermore, despite the importance of design characteristics and operational conditions on biofilter treatment performance, there is a lack of models that can be used to determine the optimal design and operation. In this paper, we developed a series of statistical models to predict the Total Phosphorus (TP) and Total Nitrogen (TN) removal performance of stormwater biofilters using various numbers of design characteristics and operational conditions. These statistical models were tested using data collected from four extensive laboratory-scale biofilter column studies. It was found that all models performed relatively well with a Nash-Sutcliffe Efficiency (NSE) of 0.42 - 0.61 for TP and 0.37 - 0.63 for TN. The most important design characteristics were filter media type and depth for TP treatment, and vegetation type and Submerged Zone depth for TN treatment. In addition, infiltration rate and inflow concentrations were the operational conditions that greatly influence outflow TP and TN concentrations from stormwater biofilters. As such, these variables need to be carefully considered when designing and operating stormwater biofilters. Sensitivity analysis results indicate that the model was quite sensitive to all regression coefficients and intercepts. Additional modelling exercises show that the model could be further simplified by reducing the number of cross-correlated parameters. These models can be used by practitioners for not just optimising the design, but also operating biofilters using real-time monitoring and control to achieve optimum performance.
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Real time control of biofilters delivers stormwater suitable for harvesting and reuse
Water research, 2019Co-Authors: Pengfei Shen, Ana Deletic, Katia Bratieres, David Thomas MccarthyAbstract:Abstract Stormwater biofilters have great potential to treat stormwater for harvesting and reuse, but their variable performance in pathogen removal requires further optimisation prior to widespread uptake. This paper provides the first evidence that real time control (RTC) of stormwater biofilters can mitigate the impact of operational characteristics that result in poor microbial removal. We developed two RTC strategies and validated them using long-term laboratory experiments, utilising biofilters with a raised outlet pipe that creates a Submerged Zone. The first RTC strategy focuses on delivering the best water quality for harvesting and reuse or for recreational waterways. It has two components which ensure adequate treatment (microbial die-off): (1) it retains water in the biofilter for at least two days before allowing any further inputs into the system, and (2) the input volume is restricted to the Submerged Zone’s pore volume. This strategy was effective and significantly improved water quality in the biofilter effluent. However, since the system favours bypassing influent to ensure good quality effluent, only 28.4% of the stormwater was treated. This still resulted in a 62.3% reduction in the influent E. coli load because the system was effective at removing E. coli under controlled conditions. The second RTC strategy builds upon the first strategy, and focuses on delivering a balance between good water quality for harvesting and protecting the environment (i.e., lower bypass). Three hours before the next rainfall event begins, the water that has remained in the biofilter’s Submerged Zone for at least two days is drained and collected for harvesting through a bottom pipe. When stormwater inflow begins, the bottom pipe is closed and the biofilter operates without control, with water leaving the biofilter to the environment via the raised outlet pipe. The harvested effluent of this RTC strategy met the Australian stormwater harvesting guideline requirements for dual reticulation with indoor and outdoor use and irrigation of commercial food crops. Although only 5.4% of stormwater was collected for harvesting in this strategy, the environment was better protected because of a significantly reduced bypass volume. Our experiments also showed that the nutrient and sediment removal was high for both RTC strategies. This study presents the first stepping stone toward RTC of stormwater biofilters, demonstrating that these systems can deliver safe stormwater for harvesting and reuse, and for active recreational uses.
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enhancing escherichia coli removal in stormwater biofilters with a Submerged Zone balancing the impact of vegetation filter media and extended dry weather periods
Urban Water Journal, 2019Co-Authors: G I Chandrasena, Ana Deletic, Jon M Hathaway, Anna Lintern, Rebekah Henry, David Thomas MccarthyAbstract:ABSTRACTStormwater biofilters have shown promising yet variable removal of faecal microorganisms. The effects of vegetation, filter media and extended drying on the removal of Escherichia coli are ...
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Dual-mode stormwater-greywater biofilters: The impact of alternating water sources on treatment performance.
Water research, 2019Co-Authors: Natalie J. Barron, Ana Deletic, Juri Jung, Harsha Fowdar, Yao Chen, Belinda Elizabeth HattAbstract:The intermittent nature of stormwater runoff impacts the treatment performance of biofilters, also known as stormwater biofiltration or bioretention systems and raingardens. During extended dry periods, which are common even in temperate climates, plants can perish, creating unattractive and non-functional systems that might leach pollutants during the next rainfall event. The current solution is to irrigate during long dry spells, which is costly and unsustainable as biofilters become more widespread. This paper presents the development of dual-mode biofilters, where stormwater and greywater are treated within the same system. Fifty columns, utilising eight plant species, including understory and climbing ornamentals, and designs with and without a carbon source in the Submerged Zone, were subjected to alternating greywater and stormwater inflows over five months. Six sampling events investigated treatment performance across these switching inflows and an extended dry period (atypical event). Good removal of total suspended solids (>83%), biochemical oxygen demand (>86%) and some heavy metals (e.g. lead >96%) were reported irrespective of design. Plant species selection was critical for the removal of nitrogen (2 to 79%) and phosphorus (12 to 75%) under dual-mode operation. However, following the extended dry period, plants with the lowest nutrient outflow concentrations also experienced some of the highest sediment and carbon concentrations, suggesting that a mixture of plant species may be beneficial for withstanding abnormal conditions. Differences between the treatment performance of designs with and without a carbon source were negligible, with potential benefits possibly negated due to the increased root mass that comes with age (systems were approximately two years old) and the release of carbon from root exudates. The results demonstrate the potential for dual-mode stormwater-greywater biofilters as an alternative to single-mode systems as they can provide effective treatment, along with greater volumes of treated water, while maintaining system performance throughout the year.
David Thomas Mccarthy - One of the best experts on this subject based on the ideXlab platform.
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The impact of stormwater biofilter design and operational variables on nutrient removal - a statistical modelling approach.
Water research, 2020Co-Authors: Kefeng Zhang, G I Chandrasena, Tracey Pham, Emily Payne, Ana Deletic, David Thomas Mccarthy, Yizhou Liu, Belinda E. Hatt, Behzad JamaliAbstract:Abstract Biofiltration systems can help mitigate the impact of urban runoff as they can treat, retain and attenuate stormwater. It is important to select the optimal design characteristics of biofilters (e.g., vegetation, filter media depth) to ensure high treatment performance. Operational conditions (e.g., infiltration rate) can also lead to significant changes in biofilter treatment performance over time. The impact of specific operational conditions on water quality treatment performance of stormwater biofilters is still not well understood. Furthermore, despite the importance of design characteristics and operational conditions on biofilter treatment performance, there is a lack of models that can be used to determine the optimal design and operation. In this paper, we developed a series of statistical models to predict the Total Phosphorus (TP) and Total Nitrogen (TN) removal performance of stormwater biofilters using various numbers of design characteristics and operational conditions. These statistical models were tested using data collected from four extensive laboratory-scale biofilter column studies. It was found that all models performed relatively well with a Nash-Sutcliffe Efficiency (NSE) of 0.42 - 0.61 for TP and 0.37 - 0.63 for TN. The most important design characteristics were filter media type and depth for TP treatment, and vegetation type and Submerged Zone depth for TN treatment. In addition, infiltration rate and inflow concentrations were the operational conditions that greatly influence outflow TP and TN concentrations from stormwater biofilters. As such, these variables need to be carefully considered when designing and operating stormwater biofilters. Sensitivity analysis results indicate that the model was quite sensitive to all regression coefficients and intercepts. Additional modelling exercises show that the model could be further simplified by reducing the number of cross-correlated parameters. These models can be used by practitioners for not just optimising the design, but also operating biofilters using real-time monitoring and control to achieve optimum performance.
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Real time control of biofilters delivers stormwater suitable for harvesting and reuse
Water research, 2019Co-Authors: Pengfei Shen, Ana Deletic, Katia Bratieres, David Thomas MccarthyAbstract:Abstract Stormwater biofilters have great potential to treat stormwater for harvesting and reuse, but their variable performance in pathogen removal requires further optimisation prior to widespread uptake. This paper provides the first evidence that real time control (RTC) of stormwater biofilters can mitigate the impact of operational characteristics that result in poor microbial removal. We developed two RTC strategies and validated them using long-term laboratory experiments, utilising biofilters with a raised outlet pipe that creates a Submerged Zone. The first RTC strategy focuses on delivering the best water quality for harvesting and reuse or for recreational waterways. It has two components which ensure adequate treatment (microbial die-off): (1) it retains water in the biofilter for at least two days before allowing any further inputs into the system, and (2) the input volume is restricted to the Submerged Zone’s pore volume. This strategy was effective and significantly improved water quality in the biofilter effluent. However, since the system favours bypassing influent to ensure good quality effluent, only 28.4% of the stormwater was treated. This still resulted in a 62.3% reduction in the influent E. coli load because the system was effective at removing E. coli under controlled conditions. The second RTC strategy builds upon the first strategy, and focuses on delivering a balance between good water quality for harvesting and protecting the environment (i.e., lower bypass). Three hours before the next rainfall event begins, the water that has remained in the biofilter’s Submerged Zone for at least two days is drained and collected for harvesting through a bottom pipe. When stormwater inflow begins, the bottom pipe is closed and the biofilter operates without control, with water leaving the biofilter to the environment via the raised outlet pipe. The harvested effluent of this RTC strategy met the Australian stormwater harvesting guideline requirements for dual reticulation with indoor and outdoor use and irrigation of commercial food crops. Although only 5.4% of stormwater was collected for harvesting in this strategy, the environment was better protected because of a significantly reduced bypass volume. Our experiments also showed that the nutrient and sediment removal was high for both RTC strategies. This study presents the first stepping stone toward RTC of stormwater biofilters, demonstrating that these systems can deliver safe stormwater for harvesting and reuse, and for active recreational uses.
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enhancing escherichia coli removal in stormwater biofilters with a Submerged Zone balancing the impact of vegetation filter media and extended dry weather periods
Urban Water Journal, 2019Co-Authors: G I Chandrasena, Ana Deletic, Jon M Hathaway, Anna Lintern, Rebekah Henry, David Thomas MccarthyAbstract:ABSTRACTStormwater biofilters have shown promising yet variable removal of faecal microorganisms. The effects of vegetation, filter media and extended drying on the removal of Escherichia coli are ...
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Stormwater Biofilters as Barriers against Campylobacter jejuni, Cryptosporidium Oocysts and Adenoviruses; Results from a Laboratory Trial
Water, 2017Co-Authors: G I Chandrasena, Ana Deletic, Anna Lintern, Rebekah Henry, David Thomas MccarthyAbstract:Biofilters are a widely used stormwater treatment technology. However; other than some evidence regarding non-pathogenic indicator microorganisms; there are significant knowledge gaps in the capacity of stormwater biofilters to remove actual pathogens and how this removal is impacted by biofilter design elements and operational conditions. In this study; we explored the capacity of stormwater biofilters to remove three reference pathogens (Campylobacter spp.; adenovirus and Cryptosporidium oocysts) and compared these to commonly used indicator microorganisms (E. coli; FRNA coliphages and Clostridium perfringens). Two different biofilter designs; each having a Submerged Zone (SZ); were tested under extended dry weather periods (up to 4 weeks) and different event volumes (the equivalent of 1–2 pore volumes) in a laboratory trial. These systems were able to consistently reduce the concentrations of all tested reference pathogens (average log reduction in Campylobacter spp. = 0.7; adenovirus = 1.0 and Cryptosporidium oocysts = 1.7) and two of the indicators (average log reduction in E. coli = 1.2 and C. perfringens = 2.1). However; none of the tested indicators consistently mimicked the removal performance of their corresponding reference pathogens after extended dry weather periods and during larger simulated storm events. This indicates that the behaviour of these pathogens in stormwater biofilters are not adequately represented by their corresponding indicator microorganisms and that to optimise biofilter designs for pathogen removal it is critical to further study pathogen removal processes in these systems.
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Stormwater biofilters: A new validation modelling tool
Ecological Engineering, 2016Co-Authors: Kefeng Zhang, Ana Deletic, Anja Randelovic, Declan Page, David Thomas MccarthyAbstract:Abstract Stormwater biofilters must be validated before they can be a trusted component of the treatment train used for water supply augmentation. Currently, only in situ challenge testing is accepted for treatment validation, yet this is impractical for stormwater biofilters because of their size and operational conditions; e.g. stormwater harvesting biofilters are often large systems that receive significant volumes of urban stormwater during short periods of time. This study proposes an alternative validation tool for stormwater biofilters that uses a process-based model calibrated against in situ tracer and laboratory based data. The method is developed and tested using fluorescein as the reference micropollutant at two different biofilters: (i) a well-designed system that uses sand as filter media and has a Submerged Zone (S-SZ), and (ii) a system with loamy sand (with content of silt and clay well above best practice), which does not have a Submerged Zone (LS-noSZ). Firstly, a model that can simulate hydrodynamic and pollutant transport of micropollutants in stormwater biofilters was selected. In situ tracer tests and laboratory batch studies were then performed to derive the model parameters using soil samples collected from the two biofilters. Without further calibration, the model was applied to simulate a number of in situ fluorescein challenge tests performed on the biofilters. The modelled outflow concentrations were compared with the in situ measurements, showing that the proposed alternative validation method could provide reliable predictions of fluorescein removal in the S-SZ, with predicted outflow concentrations agreeable to the measured data (Nash Sutcliffe coefficient, E = 0.67). The peak outflow concentrations that are important for validation study were particularly well modelled; the differences between the modelled and measured peak values were −3.9% to +7.4% for spiking tests and −4.4% to 28% for flushing/rinsing tests. However, for LS-noSZ, the proposed tool did not work well ( E = −1.7), which was attributed to the fact that flow through this system could not be reliably modelled due to high silt and clay content in the soil. The differences of peak concentrations of LS-noSZ were between −3.6% (under-predicted) and +76% (over-predicted).
Maria Viklander - One of the best experts on this subject based on the ideXlab platform.
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Phosphorus and TSS Removal by Stormwater Bioretention: Effects of Temperature, Salt, and a Submerged Zone and Their Interactions
Water Air & Soil Pollution, 2020Co-Authors: Laila C. Søberg, Maria Viklander, Ahmed M. Al-rubaei, Godecke-tobias BleckenAbstract:To prevent deterioration of receiving water bodies, phosphorus and total suspended solid (TSS) removal from stormwater is commonly targeted, e.g., by bioretention. However, their removal may vary due to ambient conditions and design features. In this study, the effect of a Submerged Zone with embedded carbon source (SZC), temperature, and (road) salt on phosphorus removal was investigated using a two-level full factorial design. A sand-based filter material was used. Overall, phosphorus and TSS removal percentages were high. Higher temperature (4.6 vs. 17.1 °C) caused higher outflow concentrations, thus lowering removal rates. The presence of salt deteriorated total phosphorus removal, whereas dissolved phosphorus removal was not affected. The impact of the SZC was statistically significant but not regarded to be of practical significance for P removal. In contrast, TSS removal was enhanced by a SZC. The results demonstrated that a relatively simple filter material could provide excellent P removal, avoiding the need for additives suggested in other studies.
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Nitrogen removal in stormwater bioretention facilities: effect of drying, temperature and Submerged Zone
2019Co-Authors: Laila C. Søberg, Godecke T Blecken, Maria ViklanderAbstract:Nitrogen removal in stormwater bioretention facilities: effect of drying, temperature and Submerged Zone
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Reduction of Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa in stormwater bioretention: Effect of drying, temperature and Submerged Zone
Journal of Hydrology X, 2019Co-Authors: Laila C. Søberg, Maria Viklander, Godecke-tobias Blecken, Annelie HedströmAbstract:Abstract The impact of drying and temperature on the reduction of Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa in stormwater bioretention systems with and without a Submerged Zone was assessed using 16 pilot-scale bioretention columns under controlled laboratory conditions. The experimental design enabled analysis of possible interactions between the factors. First outflow and event-based samples were collected. Outflow concentrations were independent of inflow concentrations and hence controlled by internal processes. Overall TSS removal was high but sensitive to bacterial synthesis. Event-based samples had significantly higher bacteria concentrations than first outflow samples, suggesting that remaining/surviving bacteria in the bioretention cells have little effect on initial peak outflow concentrations. The effect of temperature varied between bacterial species and sample types. Long dry periods seemed beneficial for bacteria reduction, but outflow bacteria concentrations peaked during the second watering after long dry periods. Submerged Zones significantly reduced bacteria outflow concentrations. However, sudden temperature increases caused bioretention cells with a Submerged Zone to produce significantly higher bacteria outflow concentrations than before the temperature increase, which was not the case for standard cells. Bioretention cells with Submerged Zones may thus be poor choices for reducing bacterial concentrations in stormwater runoff in areas experiencing winter conditions. Finally, our results suggest that adsorption (e.g. further enhanced by biofilm formation) is the major mechanism governing bacteria reduction in bioretention systems.
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Do salt and low temperature impair metal treatment in stormwater bioretention cells with or without a Submerged Zone
The Science of the total environment, 2016Co-Authors: Laila C. Søberg, Maria Viklander, Godecke-tobias BleckenAbstract:Although seasonal temperature changes and (road) salt in winter and/or coastal stormwater runoff might interfere with the metal treatment performance of stormwater bioretention cells, no previous study has evaluated the effect of these factors and their interactions under controlled conditions. In this 18week long study 24 well established pilot-scale bioretention columns were employed to evaluate the individual and combined effect(s) of low/high temperature, salt and presence of a Submerged Zone with an embedded carbon source on metal removal using a three factor, two-level full factorial experimental design. In most instances, the three factors significantly influenced the metal outflow concentrations and thus the treatment performance; the effect of temperature depended on the metal in question, salt had an overall negative effect and the Submerged Zone with carbon source had an overall positive effect. Despite these statistically significant effects, the discharge water quality was generally markedly improved. However, leaching of dissolved Cu and Pb did occur, mainly from bioretention cells dosed with salt-containing stormwater. The highest concentrations of metals were captured in the top layer of the filter material and were not significantly affected by the three factors studied. Overall, the results confirmed that bioretention provides a functioning stormwater treatment option in areas experiencing winter conditions (road salt, low temperatures) or coastal regions (salt-laden stormwater). However, validation of these results in the field is recommended, especially focusing on dissolved metal removal, which may be critically affected under certain conditions.
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Effect of retrofitting a saturated Zone om the performance of biofiltration for heavy metal removal : preliminary results of a laboratory study
2010Co-Authors: Godecke-tobias Blecken, Ana Deletic, Yaron Zinger, Timothy David Fletcher, Maria ViklanderAbstract:Stormwater biofilters are a stormwater treatment technology which has been becoming increasingly popular. Recently it has been shown that a Submerged Zone in the filter media improves the magnitude ...
Kefeng Zhang - One of the best experts on this subject based on the ideXlab platform.
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The effect of intermittent drying and wetting stormwater cycles on the nutrient removal performances of two vegetated biofiltration designs.
Chemosphere, 2020Co-Authors: Yaron Zinger, Tim D. Fletcher, Kefeng Zhang, Veljko Prodanovic, Ana DeleticAbstract:Vegetated biofiltration systems (biofilters) are now a well-established technology for treatment of urban stormwater, typically showing high nutrient uptake. However, the impact of high temporal variability of rainfall events (further exacerbated by climate change) on nitrogen and phosphorus removal processes, within different biofiltration designs, is still unknown. Hence, a laboratory-based study was conducted to uncover mechanisms behind nutrient removal in biofilters across different drying and wetting regimes. Two sets of experimental columns were based on (1) the standard biofiltration design (unsaturated Zone only), and (2) combination of unsaturated and saturated (Submerged) Zone (SZ) with additional carbon source. Columns were watered with synthetic stormwater according to three drying and wetting schemes, exploring 1, 2, 3, 4 and 7-week drying. Hydraulic performance, soil moisture and pollutant removal were monitored. The results show that hydraulic conductivity of SZ design experiences less change over time compared to standard design, due to slower media drying, crack formation and lower plant die-off. Varied drying lengths challenged both designs differently, with 2-week drying resulting in significant drop of performance across most pollutants in standard design (except ammonia), while SZ design was able to retain high performance for up to four weeks of drying, sustaining microbial and plant uptake. Increased oxygenation of SZ columns during short-term drying was beneficial for ammonia and phosphorus removal. While SZ design showed better performance and quicker recovery for nitrogen removal, in regions with inter-rain event shorter than two weeks, the standard design (no saturated Zone, no carbon source) can achieve similar if not better results.
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The impact of stormwater biofilter design and operational variables on nutrient removal - a statistical modelling approach.
Water research, 2020Co-Authors: Kefeng Zhang, G I Chandrasena, Tracey Pham, Emily Payne, Ana Deletic, David Thomas Mccarthy, Yizhou Liu, Belinda E. Hatt, Behzad JamaliAbstract:Abstract Biofiltration systems can help mitigate the impact of urban runoff as they can treat, retain and attenuate stormwater. It is important to select the optimal design characteristics of biofilters (e.g., vegetation, filter media depth) to ensure high treatment performance. Operational conditions (e.g., infiltration rate) can also lead to significant changes in biofilter treatment performance over time. The impact of specific operational conditions on water quality treatment performance of stormwater biofilters is still not well understood. Furthermore, despite the importance of design characteristics and operational conditions on biofilter treatment performance, there is a lack of models that can be used to determine the optimal design and operation. In this paper, we developed a series of statistical models to predict the Total Phosphorus (TP) and Total Nitrogen (TN) removal performance of stormwater biofilters using various numbers of design characteristics and operational conditions. These statistical models were tested using data collected from four extensive laboratory-scale biofilter column studies. It was found that all models performed relatively well with a Nash-Sutcliffe Efficiency (NSE) of 0.42 - 0.61 for TP and 0.37 - 0.63 for TN. The most important design characteristics were filter media type and depth for TP treatment, and vegetation type and Submerged Zone depth for TN treatment. In addition, infiltration rate and inflow concentrations were the operational conditions that greatly influence outflow TP and TN concentrations from stormwater biofilters. As such, these variables need to be carefully considered when designing and operating stormwater biofilters. Sensitivity analysis results indicate that the model was quite sensitive to all regression coefficients and intercepts. Additional modelling exercises show that the model could be further simplified by reducing the number of cross-correlated parameters. These models can be used by practitioners for not just optimising the design, but also operating biofilters using real-time monitoring and control to achieve optimum performance.
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Stormwater biofilters: A new validation modelling tool
Ecological Engineering, 2016Co-Authors: Kefeng Zhang, Ana Deletic, Anja Randelovic, Declan Page, David Thomas MccarthyAbstract:Abstract Stormwater biofilters must be validated before they can be a trusted component of the treatment train used for water supply augmentation. Currently, only in situ challenge testing is accepted for treatment validation, yet this is impractical for stormwater biofilters because of their size and operational conditions; e.g. stormwater harvesting biofilters are often large systems that receive significant volumes of urban stormwater during short periods of time. This study proposes an alternative validation tool for stormwater biofilters that uses a process-based model calibrated against in situ tracer and laboratory based data. The method is developed and tested using fluorescein as the reference micropollutant at two different biofilters: (i) a well-designed system that uses sand as filter media and has a Submerged Zone (S-SZ), and (ii) a system with loamy sand (with content of silt and clay well above best practice), which does not have a Submerged Zone (LS-noSZ). Firstly, a model that can simulate hydrodynamic and pollutant transport of micropollutants in stormwater biofilters was selected. In situ tracer tests and laboratory batch studies were then performed to derive the model parameters using soil samples collected from the two biofilters. Without further calibration, the model was applied to simulate a number of in situ fluorescein challenge tests performed on the biofilters. The modelled outflow concentrations were compared with the in situ measurements, showing that the proposed alternative validation method could provide reliable predictions of fluorescein removal in the S-SZ, with predicted outflow concentrations agreeable to the measured data (Nash Sutcliffe coefficient, E = 0.67). The peak outflow concentrations that are important for validation study were particularly well modelled; the differences between the modelled and measured peak values were −3.9% to +7.4% for spiking tests and −4.4% to 28% for flushing/rinsing tests. However, for LS-noSZ, the proposed tool did not work well ( E = −1.7), which was attributed to the fact that flow through this system could not be reliably modelled due to high silt and clay content in the soil. The differences of peak concentrations of LS-noSZ were between −3.6% (under-predicted) and +76% (over-predicted).
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the validation of stormwater biofilters for micropollutant removal using in situ challenge tests
Ecological Engineering, 2014Co-Authors: Kefeng Zhang, David Thomas Mccarthy, Anja Randelovic, Declan Page, Ana DeleticAbstract:Stormwater harvesting is becoming a popular alternative water resource in water stressed regions. Stormwater biofilters have been recognized as being among the most promising pre-treatment technologies. In this study, a series of challenge tests were conducted as part of a validation framework of stormwater biofilters for selected micropollutants. Two biofilter configurations were studied: a configuration with loamy sand and no Submerged Zone (LS-noSZ) and another configuration that uses sand and a Submerged Zone (S-SZ). Biofilter challenge conditions were: (i) treatment volume set at 95th percentile of all treated events and (ii) the maximum and minimum durations of dry period between two events, both based on hydrology simulations using 30 years rainfall data for Melbourne. The hydraulic performance of S-SZ was stable and not affected by either prolonged wet or dry periods, while the outflow rate of LS-noSZ was largely reduced during prolonged wet periods. Biofilters had a removal efficiency of >80% for total petroleum hydrocarbons (TPHs), glyphosate, dibutyl phthalate (DBP), bis-(2-ethylhexyl) phthalate (DEHP), pyrene and naphthalene loads by both configurations under the most challenge conditions; the removal of pentachlorophenol (PCP) and phenol loads was >80% in LS-noSZ and 50–80% in S-SZ, while chloroform had load removal rates between 20% and 50%. Biofilters were less effective in removing atrazine and simazine with load removal 20–50% in LS-noSZ and <20% in S-SZ. Prolonged dry periods benefited the removal of micropollutants while very short dry periods adversely affected micropollutants removal. The study contributes to the development of the overall framework for validation of stormwater biofilters, which is required if these systems are to be applied in stormwater treatment systems for higher end water uses such as drinking water.
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Pathogen and indicator microorganism removal in field scale stormwater biofilters
2012Co-Authors: G I Chandrasena, Ana Deletic, S Filip, Kefeng Zhang, Catherine A. Osborne, David Thomas MccarthyAbstract:Knowledge of pathogen removal in stormwater biofilters has predominately been extrapolated from bacterial indicators; indeed, the removal of actual pathogens in these systems has not yet been studied. Furthermore, there is no knowledge on as to how the pathogen removal capacity varies in biofilters with different design parameters (e.g. media composition, inclusion of Submerged Zone). Hence, this study presents the performance of two field biofilter cells (with different designs) dosed with semi synthetic stormwater in removing ten faecal microorganisms, including: indicators and pathogenic bacteria, protozoa and virus. A net reduction in concentrations was observed for all pathogens and indicators, but the removal performance varied between bacteria, protozoa and viruses. Interestingly, the behaviour of the chosen bacterial pathogens was comparable to the bacterial indicators, whereas protozoan and viral pathogen removal were lower than their corresponding indicators. Biofilters containing a Submerged Zone generally had higher removal.
G I Chandrasena - One of the best experts on this subject based on the ideXlab platform.
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The impact of stormwater biofilter design and operational variables on nutrient removal - a statistical modelling approach.
Water research, 2020Co-Authors: Kefeng Zhang, G I Chandrasena, Tracey Pham, Emily Payne, Ana Deletic, David Thomas Mccarthy, Yizhou Liu, Belinda E. Hatt, Behzad JamaliAbstract:Abstract Biofiltration systems can help mitigate the impact of urban runoff as they can treat, retain and attenuate stormwater. It is important to select the optimal design characteristics of biofilters (e.g., vegetation, filter media depth) to ensure high treatment performance. Operational conditions (e.g., infiltration rate) can also lead to significant changes in biofilter treatment performance over time. The impact of specific operational conditions on water quality treatment performance of stormwater biofilters is still not well understood. Furthermore, despite the importance of design characteristics and operational conditions on biofilter treatment performance, there is a lack of models that can be used to determine the optimal design and operation. In this paper, we developed a series of statistical models to predict the Total Phosphorus (TP) and Total Nitrogen (TN) removal performance of stormwater biofilters using various numbers of design characteristics and operational conditions. These statistical models were tested using data collected from four extensive laboratory-scale biofilter column studies. It was found that all models performed relatively well with a Nash-Sutcliffe Efficiency (NSE) of 0.42 - 0.61 for TP and 0.37 - 0.63 for TN. The most important design characteristics were filter media type and depth for TP treatment, and vegetation type and Submerged Zone depth for TN treatment. In addition, infiltration rate and inflow concentrations were the operational conditions that greatly influence outflow TP and TN concentrations from stormwater biofilters. As such, these variables need to be carefully considered when designing and operating stormwater biofilters. Sensitivity analysis results indicate that the model was quite sensitive to all regression coefficients and intercepts. Additional modelling exercises show that the model could be further simplified by reducing the number of cross-correlated parameters. These models can be used by practitioners for not just optimising the design, but also operating biofilters using real-time monitoring and control to achieve optimum performance.
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enhancing escherichia coli removal in stormwater biofilters with a Submerged Zone balancing the impact of vegetation filter media and extended dry weather periods
Urban Water Journal, 2019Co-Authors: G I Chandrasena, Ana Deletic, Jon M Hathaway, Anna Lintern, Rebekah Henry, David Thomas MccarthyAbstract:ABSTRACTStormwater biofilters have shown promising yet variable removal of faecal microorganisms. The effects of vegetation, filter media and extended drying on the removal of Escherichia coli are ...
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Stormwater Biofilters as Barriers against Campylobacter jejuni, Cryptosporidium Oocysts and Adenoviruses; Results from a Laboratory Trial
Water, 2017Co-Authors: G I Chandrasena, Ana Deletic, Anna Lintern, Rebekah Henry, David Thomas MccarthyAbstract:Biofilters are a widely used stormwater treatment technology. However; other than some evidence regarding non-pathogenic indicator microorganisms; there are significant knowledge gaps in the capacity of stormwater biofilters to remove actual pathogens and how this removal is impacted by biofilter design elements and operational conditions. In this study; we explored the capacity of stormwater biofilters to remove three reference pathogens (Campylobacter spp.; adenovirus and Cryptosporidium oocysts) and compared these to commonly used indicator microorganisms (E. coli; FRNA coliphages and Clostridium perfringens). Two different biofilter designs; each having a Submerged Zone (SZ); were tested under extended dry weather periods (up to 4 weeks) and different event volumes (the equivalent of 1–2 pore volumes) in a laboratory trial. These systems were able to consistently reduce the concentrations of all tested reference pathogens (average log reduction in Campylobacter spp. = 0.7; adenovirus = 1.0 and Cryptosporidium oocysts = 1.7) and two of the indicators (average log reduction in E. coli = 1.2 and C. perfringens = 2.1). However; none of the tested indicators consistently mimicked the removal performance of their corresponding reference pathogens after extended dry weather periods and during larger simulated storm events. This indicates that the behaviour of these pathogens in stormwater biofilters are not adequately represented by their corresponding indicator microorganisms and that to optimise biofilter designs for pathogen removal it is critical to further study pathogen removal processes in these systems.
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e coli removal in laboratory scale stormwater biofilters influence of vegetation and Submerged Zone
Journal of Hydrology, 2014Co-Authors: G I Chandrasena, Tracey Pham, Emily Payne, Ana Deletic, David Thomas MccarthyAbstract:Biofilters, also known as bioretention areas or raingardens, are an effective treatment option for the removal of various pollutants from stormwater. However, they show variable treatment efficiency for the removal of indicator bacteria, and the operational and design factors which impact this variability are largely unknown. This study uses a laboratory scale column set-up to explore how Escherichia coli (the chosen indicator organism) removal in the stormwater biofilters is impacted by: plant presence and species type, the presence of a Submerged Zone (SZ), and operational conditions (duration of dry periods and changes over the initial stages of the system’s life-span). Vegetation selection was found to be important for E. coli removal and the highly performing plant species were associated with lower infiltration rates. Based on the current results, a biofilter planted with Leptospermum continentale, Melaleuca incana or Palmetto buffalo and comprising a SZ can be recommended for improved E. coli removal. Inclusion of SZ was found to generally enhance the removal performance; which may be explained by the contribution of microbial processes that are happening within the SZ (such as predation/competition and natural die-off). Results also suggest that the E. coli removal performance is reduced after a significant dry period, while the overall removal performance improves over time as systems mature.
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Evaluating Escherichia coli removal performance in stormwater biofilters: a preliminary modelling approach.
Water science and technology : a journal of the International Association on Water Pollution Research, 2013Co-Authors: G I Chandrasena, Ana Deletic, David Thomas MccarthyAbstract:Stormwater biofilters are not currently optimised for pathogen removal since the behaviour of these pollutants within the stormwater biofilters is poorly understood. Modelling is a common way of optimising these systems, which also provides a better understanding of the major processes that govern the pathogen removal. This paper provides an overview of a laboratory-scale study that investigated how different design and operational conditions impact pathogen removal in the stormwater biofilters. These data were then used to develop a modelling tool that can be used to optimise the design and operation of the stormwater biofilters. The model uses continuous simulations where adsorption and desorption were dominant during wet weather periods and first order die-off kinetics were significant in dry periods between the wet weather events. Relatively high Nash Sutcliffe Efficiencies (>0.5) indicate that the calibrated model is in good agreement with observed data and the optimised model parameters were comparable with values reported in the literature. The model's sensitivity is highest towards the adsorption process parameter followed by the die-off and desorption rate parameters, which implies that adsorption is the governing process of the model. Vegetation is found to have an impact on the wet weather processes since the adsorption and desorption parameters vary significantly with the different plant configurations. The model is yet to be tested against field data and needs to be improved to represent the effect of some other biofilter design configurations, such as the inclusion of the Submerged Zone.
